To prevent leak of exhaust gas from a recirculation fan without needing a design change to the recirculation fan provided on a recirculation passage in a combustion device using a burner performing recirculation of exhaust gas.
The boiler 1 comprises a can body 3 having the burner 2, a main fan 4 supplying combustion air to the burner 2, an economizer 6 provided in a flue 5 of the can body 3, the recirculation passage 9 having one end connected to the downstream side of the economizer 6 and the other end connected to a combustion air suction port 7 of the main fan 4 or a combustion air passage 8 of the burner 2, and recirculating part of exhaust gas generated by combustion of the burner 2, a recirculation fan 10 provided on the route of the recirculation passage 9, and an orifice 11 provided on the upstream side of the recirculation fan 10.
NAGABUCHI TATSURO
SUZUKI HIDENORI
MIURA PROTEC KK